Tens of thousands of people have turned out in Baghdad for the beginning of a three-day funeral march for the murdered Shia Muslim leader Ayatollah Mohammed Baqr al-Hakim.

The procession, led by a coffin carrying the remains of the religious leader's body, started in the streets of Kadhimiyah, the site of a renowned Shia mosque on the banks of the river Tigris.

Ayatollah Hakim was killed in a huge car bomb in the city of Najaf on Friday which claimed at least 94 other lives.

Iraq's most senior Shia cleric, Ayatollah Ali Sistani, has blamed the US-led forces in Iraq for not preventing the bomb and called for a greater role to be played by Iraqis in establishing their own security.

Four men have been arrested in connection with the bomb, outside one of Shia Muslim's holiest sites, which also injured at least 200 people.

The investigation into the blast is being handled by the Iraqi police.

They are trying to assess whether it is linked to the earlier bombing of the UN offices in Baghdad which killed 23 people.

Local officials say the suspects include two members of the former regime from Basra and two non-Iraqi Arabs, reportedly Saudis.

Ayatollah Hakim's body is now being transported to the Shia holy
city of Karbala, 80 kilometres (50 miles) south of Baghdad, for a similar procession, before his corpse is returned to Najaf for burial on Tuesday.

Tensions are running high in Iraq, as Iraqi Shias try to come to terms with what happened to the man who had returned to the country in May after spending more than two decades in exile in Iran.

Iraq's governing council has asked for the border with Iran to be closed to prevent a huge influx of people wanting to attend the funeral.

'Walking in martyr's path'

One of the thousands of mourners at the Baghdad procession said: "We condemn this horrible crime that has been committed by the Baathists.

"We want to tell America and Saddam and all the criminals we will keep walking in the path of the martyr."

Sunday's procession started at the huge square in front of the Kadhimiyah mosque, a yellow-brick building topped by a turquoise dome.

Several sermons were read out by imams over loudspeakers.

"Hakim was for all Iraqis - Shias, Sunnis, Kurds and Turkmen. His death is a loss for us all," said one of the speakers.